PRM marine gear ratio 2.57:1

Description

PRM750D Drop-Center hydraulic marine gearbox, gear ratio 2.57:1

The PRM 750 Drop-Center marine gearbox’s dual-shaft design and separate, identical friction plates for forward and reverse operation enable full rated power in both directions. The output shaft (flanged shaft) is 120.6 mm lower than the input shaft. The input shaft has a 17-tooth 16/32 DP spline.

Technical Specifications:

• Gear Ratio: 2.57:1
• Power Rating (Recreational Use): 9.84 hp/100 rpm
• Power rating (light professional use): 7.85 hp/100 rpm
• Output shaft rotation direction during forward travel: RH or LH
• Input shaft splines: 17 TEETH, 16/32 DP
• SAE mounting: SAE2, SAE3, SAE4, and B/W plates available separately
• Maximum allowable instantaneous speed: 4,500 rpm
• Maximum allowable continuous speed: 4,000 rpm
• Weight: 72 kg
• Gearbox oil capacity: 2.5 liters + capacity of the heat exchanger and hoses
• Heat exchanger connections: 1/2" BSP X 16 DEEP

The gear unit’s hydraulic system quickly transfers the control lever’s movement to the friction plates, and the gear unit responds rapidly to direction changes, which is important for good boat handling.

Operation and Propeller Rotation

The gear can be used with both clockwise and counterclockwise rotating propellers, making it particularly suitable for twin-engine installations. The housing is made of high-quality cast iron. The oil pump and hydraulic control valves are mounted externally for easy access.

The gearbox is extremely durable and reliable; it is also equipped with a mechanical locking device in case of a hydraulic failure. In such a case, the transmission can be locked in the drive position, allowing the boat to be safely piloted back to the harbor.

Operating pressure
Minimum – 30.34 bar (440 lb/in²), maximum – 33.44 bar (485 lb/in²). The top of the valve block has a 1/8" BSP hole and the side has an M18x1.5 threaded hole for installing a pressure gauge, if needed.
Oil cooling
The normal operating temperature of the oil should be 50–80 °C, and the temperature must not be allowed to exceed 90 °C. An oil cooler is required to maintain the correct operating temperature. The valve block has 1/2" BSP connections for installing the oil cooler.
Propeller Thrust
Both forward and reverse propeller thrust is transmitted to the output shaft bearings. The force exerted on the bearings is sufficient for all power ratings approved by the manufacturer.
Propeller Free Spinning
The output shaft of the PRM750D marine gearbox can be rotated continuously while the gearbox is in neutral. Therefore, a propeller shaft brake is not required.